OCR GCSE Biology A: Monoclonal antibodies, aseptic technique and drug development (J247)

This study guide is for OCR GCSE (9-1) Gateway Science Biology A (J247), using the specification Version 4.0 (August 2026), for first assessment in 2018. It covers four statements from topic B6.3, Monitoring and maintaining health: B6.3m, B6.3n, B6.3p and B6.3q. Statements B6.3m and B6.3n are printed in bold in the specification, which means they are tested only in the Higher Tier papers. B6.3p and B6.3q are assessed at both tiers. The rest of B6.3 (disease types, immunity, vaccination, lifestyle, cancer) is taught in other pages, so it is not repeated here.

Use it with the revision notes and the practice questions. The course hub is OCR GCSE Biology, the printable list is the checklist, and you can find weak spots with the free diagnostics.

What this unit covers

Statement	What you must be able to do	Tier
B6.3m	Describe how monoclonal antibodies are produced	Higher Tier only
B6.3n	Describe uses: detecting antigens in pregnancy testing, detecting disease (prostate cancer), and potentially treating disease by targeting cancer cells	Higher Tier only
B6.3p	Explain aseptic techniques used in culturing organisms: alcohol, flaming, autoclaving glassware and growth media, and stopping contaminants falling onto or into the media (for example working around a Bunsen burner)	Both tiers
B6.3q	Describe the discovery and development of potential new medicines, including preclinical and clinical testing	Both tiers

The mathematical outcomes for B6.3 that fit this unit are: translate between graphs and numbers, read frequency tables and bar charts, understand sampling, use a scatter diagram to spot a correlation, and calculate the cross-sectional area of a bacterial culture or a clear agar area using πr².

B6.3m How monoclonal antibodies are produced (Higher Tier only)

An antibody is a protein made by a B lymphocyte (a type of white blood cell). Its binding site fits one antigen only. A monoclonal antibody is an antibody made by a single clone of cells, so every molecule is identical and binds the same antigen. The problem is that a normal B lymphocyte makes the antibody you want but soon stops dividing. A tumour cell divides without limit but makes no useful antibody. Production combines the two.

1. Inject the antigen. A mouse is injected with the antigen you want to target. Its B lymphocytes respond by making antibodies against it.
2. Collect the lymphocytes. B lymphocytes that make the antibody are taken from the mouse, usually from the spleen.
3. Fuse. These lymphocytes are fused with tumour cells (myeloma cells). Each fused cell is a hybridoma.
4. Select. The hybridomas are screened to find the ones that make the required antibody. The rest are discarded.
5. Clone and culture. Selected hybridoma cells divide many times, giving a large clone, and are grown in large vessels.
6. Collect and purify. The identical antibodies are collected from the culture medium and purified.

A hybridoma behaves like both parent cells. From the lymphocyte it gets the ability to make one specific antibody. From the tumour cell it gets the ability to divide again and again.

Worked example. Explain why the tumour cell is needed. A normal lymphocyte cannot go on dividing for long, so it would give only a small amount of antibody. The tumour cell divides repeatedly, so the hybridoma forms a large clone that keeps making the same antibody.

B6.3n Uses of monoclonal antibodies (Higher Tier only)

Because a monoclonal antibody binds one antigen and nothing else, it can be used to find that antigen or to carry something to it.

Pregnancy testing

A pregnancy test detects the hormone hCG in urine. hCG is made by the developing embryo and placenta, so it is a signal of pregnancy. A typical test strip works like this (details vary between makes):

• The area you wet holds mobile antibodies for hCG, each attached to a coloured bead.
• If hCG is present, it binds to these antibodies. The urine carries them along the strip.
• At the test line, fixed antibodies also bind hCG. The beads collect there and a coloured line appears. A line means hCG was present.
• At the control line, fixed antibodies bind the mobile antibodies whether or not they carry hCG. This line should always appear. If it does not, the test has failed.

Detecting disease

Prostate cancer cells can raise the level of a protein called PSA in the blood. A laboratory test uses monoclonal antibodies that bind PSA to measure how much is there. A raised level does not prove cancer, because other prostate problems also raise PSA. It is a reason for further tests. Antibodies can also be labelled with a dye or radioactive marker so that they show where an antigen is, such as on a tumour.

Targeted treatment of cancer

Cancer cells carry antigens on their surface that are rare on healthy cells. A monoclonal antibody that binds one of these antigens can be attached to an anti-cancer drug. When injected, it travels in the blood and binds the cancer cells, delivering the drug directly to them.

Compared with giving the drug alone	Comment
Fewer healthy cells exposed	Less damage and fewer side effects
Smaller dose can work	The drug is concentrated where it is needed
Still not risk-free	Some healthy cells carry the antigen, and the treatment is costly

Treatment of this kind is described in the specification as a potential use, so know it as a developing approach.

B6.3p Aseptic techniques in culturing organisms

Culturing bacteria needs aseptic technique. It stops unwanted microorganisms from the air, skin and surfaces getting into your culture, and stops your culture escaping. Contaminants can overgrow the organism you are studying and spoil results. The same methods keep pathogens away from the person doing the work.

Technique	What it does
Alcohol	Wiping the bench (and hands) with alcohol-based disinfectant kills microorganisms on surfaces
Autoclaving	Glassware and growth media are heated by steam under pressure, usually at about 121 °C for around 15 minutes. The high pressure lets the steam get hotter than 100 °C, which kills bacteria and their resistant spores
Flaming	An inoculating loop is held in a Bunsen flame until red hot, then cooled in the air before touching the culture. The neck of a bottle is passed through the flame when opened and closed
Working near a Bunsen burner	The flame sets up an upward air current that carries airborne microorganisms away from the work area
Limited exposure	Lids are lifted only slightly and for the shortest time. A dish is never left open

After inoculating, the lid is held on with a few short pieces of tape, not sealed all the way round, so oxygen can still enter and dangerous anaerobic bacteria are less likely to grow. The dish is labelled and usually kept upside down so condensation does not drip onto the culture. In schools, cultures are normally incubated at about 25 °C, not body temperature, because this does not favour human pathogens. A control plate that is not inoculated shows whether your technique kept it sterile.

Worked example. A student opens a Petri dish on the bench, leaving the lid off for five minutes, then notices a fuzzy colony of a different colour. Explain the cause. Airborne spores (for example from mould) fell onto the agar because the dish was open too long and not near a flame. The correct method is to lift the lid just enough to inoculate, near a Bunsen burner, then close and tape it.

Maths with cultures

Culture growth is often measured as the area covered. A colony or a clear zone is roughly circular, so area = πr², where r is half the diameter.

Worked example 1. A bacterial colony has a diameter of 9 mm. Find its area. r = 9 ÷ 2 = 4.5 mm. Area = π × 4.5² = 63.6 mm² (3 significant figures).

Worked example 2. An antibiotic disc of diameter 6 mm sits in a clear zone of diameter 24 mm. Find the area of clear agar around the disc, not counting the disc. Clear zone radius = 12 mm, disc radius = 3 mm. Area = π × 12² − π × 3² = π × (144 − 9) = π × 135 = 424 mm².

The same data can be shown as a bar chart. Check that the axes carry units and that you read from the correct bar.

B6.3q Discovery and development of new medicines

Developing a medicine is slow, costly and often fails. The aim is a drug that works, is safe, and can be given at a suitable dose.

Discovery. Many medicines began as chemicals from living things. Aspirin is related to a substance from willow bark. The heart drug digoxin comes from foxgloves. Penicillin came from the mould Penicillium. Today chemists also make and modify chemicals, then screen large numbers of candidates against cells or target molecules to find promising ones.

Preclinical testing happens before any person receives the drug:

• Cells and tissues grown in the laboratory show whether the drug has an effect and whether it is toxic.
• Computer models predict how it may behave.
• Animals are used to see the effect on a whole living body, including side effects and a safe dose. This raises ethical arguments, so only drugs that pass the earlier stages are taken forward.

Clinical testing is carried out on people:

Stage	Who	Main aim
Phase 1	Small number of healthy volunteers	Safety, and how the body handles the drug
Phase 2	Small number of patients	Does it work, best dose, side effects
Phase 3	Large number of patients	Confirm it works and is safe, compared with a placebo or the current treatment

Good trials use random allocation to groups, a placebo (a dummy treatment that looks the same), and are often double-blind, so neither patients nor doctors know who has the real drug. This stops expectation from changing the results. A larger sample reduces the effect of chance, and patients must give informed consent. Results are checked by other scientists before a medicine is approved, and effects are still monitored once it is in use.

Thalidomide is the standard warning. It was given to pregnant women for morning sickness in the 1950s and 1960s and caused limb deformities in babies. It had not been tested properly for use in pregnancy, and the case led to far stricter testing.

Worked example. In a phase 3 trial, 120 patients received the new drug and 120 received a placebo. 78 on the drug and 42 on the placebo improved. Calculate the percentage in each group who improved, and the gap between them. Drug: 78 ÷ 120 × 100 = 65%. Placebo: 42 ÷ 120 × 100 = 35%. Difference = 65 − 35 = 30 percentage points. The placebo group still improved, so some improvement is not caused by the drug. Only the 30-point gap can be credited to it.

Worked example (percentage change). Laboratory cell counts fall from 5.0 × 10⁴ cells with no drug to 3.2 × 10⁴ with the drug. Percentage change = (3.2 − 5.0) ÷ 5.0 × 100 = −36%, a decrease of 36%.

Common errors

• Saying the antibody is made by the tumour cell. The lymphocyte supplies the antibody; the tumour cell supplies unlimited division.
• Saying a pregnancy test detects the baby or an antibody. It detects the hormone hCG using antibodies.
• Forgetting the control line and what it shows.
• Writing “kills germs” for flaming. Explain what is sterilised and why (loop, bottle neck, no contaminants).
• Sealing a dish completely with tape, or incubating at body temperature, in a school context.
• Using the diameter instead of the radius in πr².
• Treating a phase 1 trial as testing whether the drug works. It is mainly about safety.
• Claiming that a placebo group “gets nothing”. It gets a dummy treatment, so any change is still recorded.

Official syllabus

OCR GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), for first assessment in 2018, published by OCR. The relevant statements are B6.3m, B6.3n, B6.3p and B6.3q.